There is an increasing demand for wireless networking devices that can be used to connect a plurality of computing devices together in a network. Most people would prefer to avoid installing the wiring that would be required for a conventional Ethernet network, due to the expense and difficulty. Newer wireless network standards, such as the 802.11g amendment to the specification established by the Institute of Electrical and Electronics Engineers (IEEE), will enable faster wireless data communication than the earlier 802.11b amendment to the specification. However, there are clearly limits in the range of communication between wireless devices, regardless of the version of the 802.11 specification that is applicable. Most manufacturers of wireless devices specify their range under optimum conditions that often do not exist in the real world. The environment in which wireless devices are used can greatly affect their usable range. For example, when brick and stone, or metal framing are employed for interior walls in the construction of homes and other buildings in which wireless devices are used, these structures substantially attenuate the wireless signals, greatly reducing the effective distance for wireless communications between wireless devices. Consequently, it may be impossible to achieve reliable wireless communications between an access point at one point in a structure and another wireless device located at a disparate point in the structure.
One way to address this problem is to install one or more additional access points, each of which are connected through appropriate Ethernet wiring to a base station or router. However, the installation of additional access points requires adding wiring, which is contrary to the purpose of using a wireless network. Accordingly, it would be preferable to employ a different approach to extend the service range of wireless devices without needing to add wiring to a structure to support additional access points. It should be possible to extend the service range of wireless communications by enabling the wireless signals to be directed around blocking walls and other structural objects within a building and by amplifying the signals.
One approach that might be used for extending the service range of wireless communications employs a repeater. Radio and television signals are often received by a repeater that then repeats the transmission of the signals to extend the coverage range of commercial stations. However, such repeaters are analog device and are typically not bi-directional, since they are designed to receive a signal from a commercial transmitter and repeat the transmission of the signal on another frequency to the receivers (radio or television) in a more distant location. Also, these unidirectional prior art analog repeaters are not usable in a packet network. Unlike the applications for the prior art analog repeaters, a wireless network must be capable of communicating data packets bi-directionally between wireless devices, while avoiding interference between an original signal and the retransmitted signal in either direction of communication.
Range extending repeaters are available for wireless networks, but they use an excessive amount of the available bandwidth. For example, D-Link Corporation's DWL-800AP+™ unit can be configured to operate as a wireless access point or as a repeater for another wireless access point or router. When used in repeater mode, this device substantially increases the demand on the available bandwidth, because it must receive packets from an access point or base station, store the packets, and then retransmit the packets to the intended recipient—on the same channel. Therefore, it takes approximately twice the time normally required to transmit packets to an intended recipient when the repeater is used. Also, the manufacturer cautions that this repeater will only work with certain “compatible access points and routers.”
It would be preferable to employ a translating retransmitter that retransmits data packets at about the same time they are received, instead of receiving the data packets, storing them, and then transmitting them in two distinct operations that do not overlap. An appropriate retransmitter should be able to receive data packets from a base station, access point, or wireless device on one channel and within microseconds, transmit the data packets received on another channel, so that there is little perceived delay in the data packets reaching the intended recipient, yet without causing interference between the data packets being received and those being retransmitted. The retransmission should occur sufficiently fast that an acknowledgement for the data packets is received from the intended recipient by the wireless device that originally transmitted the data packets sufficiently soon to avoid the wireless device considering the packets to have been lost. If the acknowledgement is not received within a defined acknowledgement time (referred to as the “ACK time”), which is about 112 microseconds for the IEEE 802.11b specification, the wireless device that originally transmitted the data packets will assume that the transmission was not received, and again transmit the data packets—wasting bandwidth and delaying communications on the wireless network. In contrast, a conventional prior art repeater that has received data packets from the original source sends an acknowledgement back to the original source of the data packets, then transmits the data packets to the intended recipient, and awaits the acknowledgement from the intended recipient. Clearly, it would be preferable to avoid having to send two separate transmission and acknowledgements over the wireless network to complete the communication. By retransmitting data packets sufficiently fast as they are being received, the source transmitter of the data packets on the local area network (LAN) should receive an acknowledgment back from the intended recipient, as if the intended recipient had received the data packets directly from the source transmitter.
Accordingly, it will be apparent that a more efficient use of the broadcast bandwidth should be possible when retransmitting data packets, than is done with prior art repeaters. By enabling the near instantaneous retransmission of data packets so that the intended recipient and the source of the data packets appear to be more nearly in direct communication, much more efficient use of the wireless LAN bandwidth is achieved. Also, data packets should be retransmitted on a different channel than that on which they are received from the original source transmitter, to avoid any interference problems between the original source wireless signal and the retransmitter wireless signal. Currently, none of the prior art wireless devices provide such functionality.